Bell tone generator

ABSTRACT

A bent bar generator is tuned to a Flemish standard by drastically changing the frequency of the first subtone so that it is precisely one octave below the prime tone instead of the usual five semitones below the prime tone, all while maintaining the tuning of the first overtone. This is done by deliberately selecting a bar length that is rather substantially sharp whereby severe tuning at selected nodal and antinodal points provides the requisite drastic shift of the relative frequency of the first subtone.

, United States Patent I Inventor Paul H. Rowe, Sn, deceased late of Vista, Calif. (by Paul H. Rowe, Jr., executor, 1825 Alpha Road, Glendale. Calif. 91208) Appl. No. 770,872

Filed Oct. 25, 1968 Patented June 29, 1971 BELL TONE GENERATOR ll Claims, 6 Drawing Figs.

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Int. Cl Field of Search [56] References Cited UNITED STATES PATENTS 2,703,504 3/1955 Rowe i. 84/402 3,013,461 12/1961 Kunz 84/402 Primary Examiner-Richard B. Wilkinson Assistant Examiner-John F. Gonzales Atmme vFlam and Flam ABSTRACT: A bent bar generator is tuned to a Flemish standard by drastically changing the frequency of the first subtone so that it is precisely one octave below the prime tone instead of the usual five semitones below the prime tone, all while maintaining the tuning of the first overtone. This is done by deliberately selecting a bar length that is rather substantially sharp whereby severe tuning at selected nodal and antinodal points provides the requisite drastic shift of the relative frequency ofthe first subtone.

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l'illliiil llu BELL TONE GENERATOR BRIEF SUMMARY OF THE INVENTION This invention relates to tone generators of the type shown and described in the U.S. Pat. Nos. 2,588,295 and 2,703,504 issued to Paul H. Rowe respectively on Mar. 4, 1952 entitled Apparatus For Producing Chime Tones And Method Of Tuning Musical Bars," and on Mar. 8, 1955 entitled,Tone Adjustment for Vibrant Bars. These patents show small string suspended bent bars. Although the sound volume produced by the bent bars is very small, the bars nevertheless exhibit the same modes of vibration as large cast bells. Accordingly, through the medium of electronic amplification, full, rich bell tones are produced but with compact tone generators.

These bent bars have characteristic modes of vibration or partials. The fourth gravest mode is usually chosen for the fundamental or prime tone. An untuncd bar having a fundamental for A, for example, has partials normally falling at positions approximately corresponding to C, (subtone), E (overtone), A (octave), and A, (second octave). The subtone and the overtone provide the minor (overtone), and fifth which are characteristic of bell tones. In order to tune the bar in ac cordance with the method outlined in said Rowe patents, the length of the bent bar is chosen so that the fundamental of the bar is about a half a semitone sharp. By carefully selecting the positions for altering the compliance of the bar and the length of the bends, the partials are brought into concordance. An excellent bell tone is provided. However, the bell tone has no significant hum tone one octave below the prime tone, and which tone is characteristic of Flemish bells.

In order to provide a Flemish bell tone with tuned bars of this type, a second set of bars has been provided. Thus, when the bar corresponding to A, is struck, a bar corresponding to A is simultaneously struck. Alternately, couplers have been proposed. While the solution is more or less satisfactory, the number of generators is increased substantially with consequent cost penalty.

The primary object of this invention is to provide a bent far having a substantial suboctave hum tone to provide the Flemish tonal characteristic while retaining the necessary minor third and fifth partials. This is accomplished by a tuning method in which the normal subtone instead of being tuned to the minor third relationship, is drastically shifted to provide a hum tone. At the same time, the second octave of the normal subtone is tuned to the minor third relationship whereby the total tonal effect has remarkable similarity to the cast Flemish bell. In order to so drastically tune the normal subtone, the bent bar has a length chosen so that the prime tone is markedly off tunein fact, between one and two semitones whereby the drastic tuning techniques can exhibit even more drastic effects on the subtone by suitably selecting the regions for alteration of bar compliance.

This invention possesses many other advantages and has other objects which may be more clearly apparent from a consideration of one embodiment of the invention. For this purpose, there is shown a form in the drawings accompanying and forming a part ofthe present specification. This form will now be described in detail, illustrating the general principles ofthe invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of this invention is best defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front elevation of an apparatus embodying the inlention.

FIG. 2 is an enlarged vertical section, taken generally along 2 line 2-2 of FIG. I.

"i. 3 is a further enlarged partial vertical section of the ...p!ifie end ofthe apparatus.

FIG. -t is a partial vertical section through a modified form ofthe invention.

FIG. 5 is a side elevational view of one of the bars, together with a diagram ofthe vibrational mode of the pitch tone.

FIG. 6 is a chart showing the progressive changes of the frequency characteristics ofseveral partials.

DETAILED DESCRIPTION In FIGS. 1 to 4 there is illustrated a frame I0 that supports a plurality of resonant bars II in spaced parallel relationship. The bars II, by way of example, may be made of one-eighth inch diameter round, mild steel bar stock. Each bar is suspended vertically by an upper hanging cord 12 and is restrained from movement at its lower end by a cord 13. The cords I2 and I3 are made of flat braided material such as nylon.

Each upper cord extends downwardly from spaced anchor screws l4, l5 threaded into the upper portion I6 of the supporting frame. The upper cord passes through a transverse hole 17 drilled through a nodal point of one of the partials. The cord has a width slightly greater than the hole in order to fit snugly thus to exert the proper damping on the other par tials of the bar. The cord passes upwardly through another anchor screw !5 and is then wound upon another tightening screw 18.

The lower cord is similarly dressed. One end is attached to a screw 19 secured to the lower portion 20 of the supporting frame it). The cord extends angularly upwardly and passes through a transverse hole 21 near the node of one of the partials. The cord extends angularly downwardly and passes about the shank of another screw 22 and into a tightening element 23 threadedly mounted by the lower portion 20 of the supporting frame.

Anchors for certain bars serve as guides for cords for adjacent bars.

The upper and lower ends ofeach bar are bent substantially at right angles to the main portion 24 of the bar, the bent ends 25 and 26 preferably being substantially coplanar. A magnetic pickup 27 is positioned above the shorter upper arm 26. The striker 28 is disposed below the lower arm 25. The striker 28 has an electromagnetically actuated plunger 29 suspended from the arm 25 by a felt loop 30 that serves as a damper. When the bar is struck, the bar undergoes lateral flexural excitation in the plane defined by the bent ends 25 and 26. The position of the pickup 27 and the striker plunger 29 is carefully selected in order to achieve the appropriate response and as set forth more fully in said prior Pat. No. 2,588,295.

When the bar is struck, there are a number of distinguishable vibrational modes including (1 a prime or pitch tone arbitrarily selected as the fourth gravest of the distinguishable tones; (2) a subtone approximately eight semitones below the pitch tone and corresponding to a minor third; (3) the first overtone which is seven semitones above the pitch tone and corresponding to the major fifth; (4) the octave of the pitch tone; and (5) the double octave of the pitch tone.

By employing tuning methods such as described in said prior Pat. No. 2,703,504, the subtone and the pitch tone, which normally are about eight semitones apart, are moved an additional four semitones apart to a full octave relationship. This can be done in a number of ways. One is to provide a bent bar that is initially quite substantially sharp. For example, to tune a one-eighth inch diameter steel bar to a pitch of C the bar is cut to a length of 19 inches. The bar is then bent such that its longer bent end 25 has an overall length of 1.347 inches measured to the outside or far side of the main portion 24 of the bar, and so that the shorter arm 26 is bent to an outside length of 1.036 inches. The inside radii of the bent ends are approximately the same diameter of the bar. Preferably the radius of curvature is as small as possible without producing incipient face fractures or excessive internal stress, which stress will manifest itself in a noticeable reduction of the resonant quality of the bent bar. The overall length of the main body 24 of the bar new measures approximately 17.093 inches. The prime tone will be found to be about L60 semitones sharp. The overtone, which is eventually to be the major fifth, will be nearly a full semitone sharp. Now the center nodal point 31 (FlG. of the prime tone is found either by chart. calculation or experiment. Nodes of the overtone are similarly located at 32 and 33. Charts showing the relative location of the nodes and antinodes of the essential partials of the bar may be determined by proportional extrapolation based upon grooves of vibrational modes depicted, for example. in Miessner No. 2.4 i 3.062.

The nodes 32 and 33 are selected so as to be far displaced from the nodes of the subtone whereby grooves at points 32 and 33 will operate effectively to lengthen the bar as to thc subtone mode of vibration to cause a reduction in frequency. However. the nodes 32 and 33 are chosen so as to be displaced only slightly from the nodal points of the second octave ofthc subtone.

The center groove 31 is filed in a broad arc until the overtone is lowered almost to its correct frequency. This filing has no substantial effect upon the prime tone and has significant effect on the bum tone whose antinode is displaced from the point 31. The grooves 32 and 33 are now filed until the prime tone is substantially at its correct pitch. The grooves at 32 and 33 have very little. if any. effect upon the overtone. but they do materially lower the frequency characteristic of the subtone.

The grooves 31. 32 and 33 are quite deep. bearing in mind the substantial deviation from true pitch of the ungrooved bar. The two grooves 32 and 33 together provide the requisite alteration in compliance without seriously weakening the barv Preferably. neither groove extends more than half way through the bar. Preferably. the grooves 32 and 33 are formed by companion grooves on opposite sides. if a square section rod is used. these considerations are not as important.

it will be found that the removal of material at the points 3 i. 32 and 33 results in the subtone moving substantially to the octave relationship below the prime tone. while the second octave ofthe subtone is merely tuned to the minor third position. Fine tuning methods well known in the art. including filing the bent ends and providing corners at the bends. are utilized to complete the tuning.

The chart (HO. 6) graphically depicts the same method as above described. but by reversing the initial order ofgrooving. The chart depicts the frequency characteristics of the partials at successive stages for a bar to be tuned to A.. Column 1 shows the frequency characteristics of the partials before grooving. Column 2 denotes the frequency ofthe partials after a groove is placed at the top nodal point 32. Column 3 denotes the frequency characteristics of the partials after a groove is provided at the bottom point 33. Column 4 denotes the frequency characteristics of the partials after a groove is providcd at the central point 3!. Column 5. 6 and 7 denote frequency characteristics after additional finc tuning steps. The chart shows that the subtone is moved from D to A... whereas the second octave of the subtone moves slightly from approximately a quarter of a semitone ttbovc D. to C... whereby the minor third characteristic is provided.

Other nodal points ofthc various partials can be selected for grooving. Moreover. the compliance of the bar may be altered by stiffening rather than in conjunction with grooving. and as described in said prior Pat. No. 2.703.504. The essential relatlonship is that the bar as originally bent exhibits a prime tone characteristic that is substantially sharp or list. whereby selec' tlve tuning produces a drastic shiit in the relative frequency relationship of the prime tone and subtone so that they move into octave concordance. Only by starting at a point seemingly unnecessarily far removed from proper tuning is it possible in this simple manner to achieve the Flemish characteristic. utilizing the subtone partial.

Tuning in accordance with the essential principle of the invcntlon has also been achieved by grooving at four points. the

node ofthc octave of the prime. the node of double octave oi the prime. and two modes ofthc overtone. in this example. the groove points have sufficient differential effects on the prime tone and subtone as to make possible the requisite shift to octavc relationship.

By suspending the bar at the nodal point of the hum tone, the bell characteristic is simulated wherein the pitch or prime tone decays more rapidly than the hum tone.

it has been found desirable to have the pickup fairly near the tips of the higher pitched bars and closer to the bends in the lower pitched bars.

The original lengths of all bars in a set can be determined experimentally or. they can be determined by calculations based upon previously tuned bars or a standard bar. The proportionality constant is applied in accordance with the ratio of the wavelengths of the prime tones. all in a well understood manner.

Utilizing the proportionality constant, it is found that the longer bent end should be about 0.0804 times the overall length of the bent bar. and the shorter bent end should be about 00593 times the overall length of the bent bar. Slight modifications will be made in this proportionality constant according to the extremes ofthe musical range where the secondary effects such as bar diameter may be taken into consideration.

I claim:

1. The method of tuning a resonant bar having a subtone corresponding substantially to a minor third and an overtone corresponding substantially to a fifth which comprises forming the bar to a predetermined length such that the selected prime tone deviates about a semitone or two from the desired nominal pitch whereby said partials deviate substantially from the desired pitch; shifting the subtone to a suboctave relationship to the prime tone while shifting the prime tone to nominal pitch by changing the compliance of the bar at preselected nodal and antinodal points along the bar.

2. The method as set forth in claim 1 in which the prime tone of the bar before tuning is approximately one and a half semitones sharp.

3. The method as set forth in claim l in which said bar also has a partial other than the subtone that corresponds to the minor third. said nodal and antinodai points being chosen to maintain the minor third component characteristic of said bar by the aid of said other partial. 4

4. The method as set forth in claim 1 in which the selected nodal and antinodal points include one or more nodal points of the overtone displaced substantially from the nodal points of the subtone.

5. The method as set forth in claim 4 in which the selected nodal and antinodal points include a nodal point of the prime tone. v

6. The method as set forth in claim 2 in which the selected nodal and antinodal points include two nodal points of the overtone each of which is displaced substantially from nodal points ofthe subtone and a nodal point of the prime tone. said compliance being altered by grooving at said selected points.

7. The method of tuning a resonant bar which comprises bending the ends ofa bar to determine a vibrational plane and provide a preselected bar length in which the third interval subtone. selected prime tone and fifth interval overtone all deviate correspondingly from their nominal frequencies. the prime tone deviating about a semitone or two; tuning the bar by changing its compliance with said vibrational plane and at selected nodal and antinodal points along the bar differentially to shift the subtone and the prime tone so that they ultimately occupy a single octave relationship with respect to each other; said deviation from nominal frequency being initially sufficient to allow said differential shift.

8. The method as set forth in claim 7 in which said bar is a rod of round cross section; said alteration ofcompliance being accomplished by grooving the bar at two nodal points of the overtone to maintain the maximum diameter of said rod. and at one nodal point ofthe prime tone 9. The method as set forth in claim 7 in which said bar also has a partial other than the subtone that corresponds to the minor third. said nodal and antinodal points being chosen to maintain the minor third component characteristic of said bar through said other partial.

10. A resonant bar having ends bent at corresponding right angles and to lengths corresponding substantially to 0.08 and 0.05 times the overall length of the bent bar with the overall length of the bent bar such as to provide, before alteration of compliance, a prime tone that is approximately one and a halt" semitones sharp; said resonant bar having a groove at one or more nodal points of the overtone to alter the bending characteristic of said bar in the plane by said bends, and having a groove at one or more nodal points of said prime tone 

1. The method of tuning a resonant bar having a subtone corresponding substantially to a minor third and an overtone corresponding substantially to a fifth which comprises forming the bar to a predetermined length such that the selected prime tone deviates about a semitone or two from the desired nominal pitch whereby said partials deviate substantially from the desired pitch; shifting the subtone to a suboctave relationship to the prime tone while shifting the prime tone to nominal pitch by changing the compliance of the bar at preselected nodal and antinodal points along the bar.
 2. The method as set forth in claim 1 in which the prime tone of the bar before tuning is approximately one and a half semitones sharp.
 3. The method as set forth in claim 1 in which said bar also has a partial other than the subtone that corresponds to the minor third, said nodal and antinodal points being chosen to maintain the minor third component characteristic of said bar by the aid of said other partial.
 4. The method as set forth in claim 1 in which the selected nodal and antinodal points include one or more nodal points of the overtone displaced substantially from the nodal points of the subtone.
 5. The method as set forth in claim 4 in which the selected nodal and antinodal points include a nodal poinT of the prime tone.
 6. The method as set forth in claim 2 in which the selected nodal and antinodal points include two nodal points of the overtone each of which is displaced substantially from nodal points of the subtone and a nodal point of the prime tone, said compliance being altered by grooving at said selected points.
 7. The method of tuning a resonant bar which comprises bending the ends of a bar to determine a vibrational plane and provide a preselected bar length in which the third interval subtone, selected prime tone and fifth interval overtone all deviate correspondingly from their nominal frequencies, the prime tone deviating about a semitone or two; tuning the bar by changing its compliance with said vibrational plane and at selected nodal and antinodal points along the bar differentially to shift the subtone and the prime tone so that they ultimately occupy a single octave relationship with respect to each other; said deviation from nominal frequency being initially sufficient to allow said differential shift.
 8. The method as set forth in claim 7 in which said bar is a rod of round cross section; said alteration of compliance being accomplished by grooving the bar at two nodal points of the overtone to maintain the maximum diameter of said rod, and at one nodal point of the prime tone
 9. The method as set forth in claim 7 in which said bar also has a partial other than the subtone that corresponds to the minor third, said nodal and antinodal points being chosen to maintain the minor third component characteristic of said bar through said other partial.
 10. A resonant bar having ends bent at corresponding right angles and to lengths corresponding substantially to 0.08 and 0.05 times the overall length of the bent bar with the overall length of the bent bar such as to provide, before alteration of compliance, a prime tone that is approximately one and a half semitones sharp; said resonant bar having a groove at one or more nodal points of the overtone to alter the bending characteristic of said bar in the plane by said bends, and having a groove at one or more nodal points of said prime tone similarly to alter the bending characteristic of said bar; said grooves being of such depth as to provide a subtone shifted from a third interval relationship downwardly to an octave relationship with respect to said tone whereby a Flemish bell characteristic is provided.
 11. The resonant bar as set forth in claim 10 in which said nodal points are so located as to provide a significant partial having a third musical interval relationship to said prime tone. 